Hex Bolt is divided into three grades: A, B and C

There are two types of bolted connections: ordinary bolted connections and high-strength bolted connections. Ordinary bolts are classified into A, B, and C grades.

Grades A and B are refined bolts, and Grade C is rough bolts. Grade A and B refined bolts have smooth surfaces, accurate dimensions, high requirements for hole quality, complex production and installation, and high prices, which are rarely used in steel structures. The difference between grades A and B refined bolts is only the length of the bolt shank. Class C bolts are generally used in connections in tension along the shank axis, as well as for shear connections of secondary structures or for temporary fixation during installation.

Since pier heads are mostly required in bolt production, most bolt steels are Cold Heading Wire Rod. With the enlargement of cold pier equipment or the high speed of production, the requirements for cold pier steel are also increasing. Bolts play the roles of connection, fastening, positioning, and sealing in the mechanism. With the exception of the simple positioning bolts, the Hex Bolt is pre-tightened during installation and therefore is subject to static tensile loads. Some bolts, such as connecting rod bolts, cylinder head bolts, etc., are usually subjected to additional axial tensile (alternating) loads, transverse shear ( Alternating) loads or the resulting composite bending loads, and sometimes shock loads. Usually, the additional transverse alternating load will cause loosening of the bolt, the axial alternating load will cause the fatigue fracture of the bolt, and the axial tensile load under the action of the environmental medium will cause the delayed fracture of the bolt.